At the time of the setting of "I Stand Here Ironing," divorce was not common, nor was the abandonment of a father from his family. So, when Emily's mother is separated from her husband she feels especially bereft and guilty. Without other single-mother families to whom Emily can identify, she feels isolated, abandoned.
In addition, the Depression-era generation never forgot what deprivation they experienced despite the comfortable economic times of the 1950, so there was a large "generation gap" between them and their children who knew little of such deprivation. As a consequence, Emily does not understand her mother's having to relinquish her to a home and the lack of time that her mother had for her.